Engineering a CsPbBr3-based nanocomposite for efficient photocatalytic CO2 reduction: Improved charge separation concomitant with increased activity sites

Article abstract of DOI:10.1039/c9ra07236e

Metal-halide perovskite nanocrystals have emerged as one of the promising photocatalysts in the photocatalysis field owing to their low-cost and excellent optoelectronic properties. However, this type of nanocrystals generally displays low activity in photocatalytic CO₂ reduction owing to the lack of intrinsic catalytic sites and insufficient charge separation. Herein, we functionalized CsPbBr₃ nanocrystals with graphitic carbon nitride, containing titanium-oxide species (TiO-CN) to develop an efficient composite catalyst system for photocatalytic CO₂ reduction using water as the electron source. Compared to its congener with pristine CsPbBr₃, the introduction of TiO-CN could not only increase the number of active sites, but also led to a swift interfacial charge separation between CsPbBr₃ and TiO-CN due to their favorable energy-offsets and strong chemical bonding behaviors, which endowed this composite system with an obviously enhanced photocatalytic activity in the reduction of CO₂ to CO with water as the sacrificial reductant. Over 3-fold and 6-fold higher activities than those of pristine CsPbBr₃ nanocrystals and TiO-CN nanosheets, respectively, were observed under visible light irradiation. Our study provides an effective strategy for improving the photocatalytic activity of metal-halide perovskite nanocrystals, thus promoting their photocatalytic application in the field of artificial photosynthesis.

Full text of DOI:10.1039/c9ra07236e

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Engineering a CsPbBr3-based nanocomposite for
efficient photocatalytic CO2 reduction: improved
charge separation concomitant with increased
activity sites†
Cite this: RSC Adv., 2019, 9, 34342
Xiao-Xuan Guo,a Shang-Feng Tang,a Yan-Fei Mu,a Li-Yuan Wu,a Guang-Xing Donga
ab
*
and Min Zhang
Metal-halide perovskite nanocrystals have emerged as one of the promising photocatalysts in the
photocatalysis field owing to their low-cost and excellent optoelectronic properties. However, this type
of nanocrystals generally displays low activity in photocatalytic CO2 reduction owing to the lack of
intrinsic catalytic sites and insufficient charge separation. Herein, we functionalized CsPbBr3 nanocrystals
with graphitic carbon nitride, containing titanium-oxide species (TiO-CN) to develop an efficient
composite catalyst system for photocatalytic CO2 reduction using water as the electron source.
Compared to its congener with pristine CsPbBr3, the introduction of TiO-CN could not only increase the
number of active sites, but also led to a swift interfacial charge separation between CsPbBr3 and TiO-CN
due to their favorable energy-offsets and strong chemical bonding behaviors, which endowed this
composite system with an obviously enhanced photocatalytic activity in the reduction of CO2 to CO
with water as the sacrificial reductant. Over 3-fold and 6-fold higher activities than those of pristine
CsPbBr3 nanocrystals and TiO-CN nanosheets, respectively, were observed under visible light irradiation.
Our study provides an effective strategy for improving the photocatalytic activity of metal-halide
perovskite nanocrystals, thus promoting their photocatalytic application in the field of artificial
photosynthesis.
Received 9th September 2019
Accepted 7th October 2019
DOI: 10.1039/c9ra07236e
rsc.li/rsc-advances
photocatalysts19–31 owing to their high defect tolerance and low-
cost as well as the facile processing methods,32–35 which have
been dramatically exploited in optoelectronic devices.36–39
Introduction
Sunlight-driven photocatalytic CO2 conversion into high-value
added fuels or chemical feedstocks is generally perceived as
a promising solution to simultaneously alleviate both energy
crisis and environmental problems and has received intense
attention in the eld of articial photosynthesis.1–5 In recent
years, most of the attention on this technology has been focused
on the development of cost-effective photocatalyst systems.6–14
In this regard, semiconductor nanocrystals possess excellent
properties, such as nely tunable band gaps, large extinction
coefficients and long photogenerated carrier lifetimes, and have
been actively pursued as photocatalysts in the eld of photo-
catalysis.15–18 Most recently, metal-halide perovskite nano-
crystals, a type of fascinating semiconductor candidates for
sunlight harvesting, have also emerged as a class of promising
In the eld of photocatalytic CO2 reduction, however, almost
all the pristine metal-halide perovskite nanocrystal photo-
catalysts exhibit poor photocatalytic activity owing to the lack of
intrinsic catalytic sites and insufficient charge separa-
tion.20,22,24,27,29,31 As a learning from the previous studies on
conventional metal chalcogenide semiconductor nanocrystals,
loading metal-halide perovskite nanocrystals on some two-
dimensional (2D) materials, such as graphene oxide30 or
graphitic carbon nitride22 (g-C3N4), is expected to enhance the
charge separation efficiency, leading to improved photocatalytic
activity in CO2 reduction. However, the lack of intrinsic catalytic
sites in these 2D materials also limits the further improvement
in their photocatalytic performance in CO2 reduction. Indeed,
our preliminary experiment showed that the CsPbBr3@g-C3N4
composite photocatalyst exhibit a little improvement in pho-
tocatalytic activity for CO2 reduction compared to pristine
CsPbBr3 under the irradiation of visible light. It is known that
the polymeric material g-C3N4 is a good support material for
single atom40–47 and metal nanoparticles,48–50 and enhanced
aInstitute for New Energy Materials and Low-Carbon Technologies, Tianjin University
of Technology, Tianjin, 300384, China. E-mail: zm2016@email.tjut.edu.cn
bTianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School
of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin,
300384, China
† Electronic supplementary information (ESI) available: Additional data and
experimental details. See DOI: 10.1039/c9ra07236e
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solar fuel production can be achieved along with the introduc-
tion of these metal catalytic sites.
On the basis of the above analysis, to simultaneously
increase the number of catalytic sites and improve the charge
separation efficiency of the CsPbBr3-based photocatalyst for
CO2 reduction, herein, we functionalized the CsPbBr3 nano-
crystals with graphitic carbon nitride nanosheets, containing
titanium-oxide species (TiO-CN), to develop an efficient
composite photocatalytic system (coded as CsPbBr3@TiO-CN)
for photocatalytic CO2 reduction. Structural characterization
revealed that the CsPbBr3 nanocrystals were closely anchored
on 2D TiO-CN via N–Br and O–Br bonding, as discussed below.
We further systematically compared its structure, light-
harvesting ability, band gap alignment, charge generation and
separation, as well as the photocatalytic activity in CO2 reduc-
tion, with those of the reference photocatalysts based on pris-
tine CsPbBr3 nanocrystals and TiO-CN nanosheets.
Result and discussion
The 2D nanosheets of TiO-CN were prepared according to the
method described in a previous publication,47 which is based on
a
Fig. 1 TEM images of TiO-CN (a) without and (b) with CsPbBr3
nanocrystal loading. The black dots in panel b are the CsPbBr3
nanocrystals, and the particle size distribution of CsPbBr3 is given in
the inset in panel b. (c) HRTEM image with the lattice spacing of
monoclinic CsPbBr3 on TiO-CN. (d) XRD patterns of TiO-CN, CsPbBr3
and CsPbBr3@TiO-CN.
simple dicyandiamide blowing method.51 The pristine
CsPbBr3 nanocrystals were synthesized according to a pub-
lished procedure using a conventional hot injection approach.52
The CsPbBr3@TiO-CN composite was obtained by simply mix-
ing CsPbBr3 nanocrystals and TiO-CN nanosheets in hexane
solvent. The detailed procedure is described in the ESI.† Briey,
CsPbBr3 nanocrystals and TiO-CN nanosheets were rst added
into hexane solvent. Aer ultrasonication for 15 minutes and
successive stirring for 2 hours, the color of the solution changed
from yellow-green to colorless (Fig. S1†), implying that the
CsPbBr3 nanocrystals dispersed in hexane were successfully
loaded onto the TiO-CN nanosheets. Then, the CsPbBr3@TiO-
CN composite was obtained aer centrifugation, followed by
drying.
The morphology and composition of the CsPbBr3 nano-
crystals on TiO-CN nanosheets were rst evaluated by trans-
mission electron microscopy (TEM) and high-resolution
transmission electron microscopy (HRTEM) measurements. As
shown in Fig. 1a and b, the CsPbBr3 nanocrystals could be
clearly observed on the sheet-like TiO-CN. The average size of
the CsPbBr3 nanocrystals on TiO-CN was approximately 15 nm
(Fig. 1b), which is similar to that of the as-prepared CsPbBr3
nanocrystals (Fig. S2†). The HRTEM image of the CsPbBr3
nanocrystals on TiO-CN (Fig. 1c) showed a clear lattice spacing
of 0.58 nm, corresponding to that of the (100) plane in the
monoclinic CsPbBr3 phase.53 As further demonstrated in
Fig. 1d, the X-ray diffraction (XRD) pattern of the CsPbBr3
nanocrystals displayed typical diffraction peaks for monoclinic
CsPbBr3, which could be well tted to the standard pattern of
JCPDS 00-018-0364. In addition, the XRD pattern of TiO-CN
(Fig. 1d) was similar to that of g-C3N4, which is consistent
with a previous result.47 Moreover, the diffraction peaks of both
CsPbBr3 nanocrystals and TiO-CN nanosheets could be clearly
observed in the XRD pattern of the CsPbBr3@TiO-CN composite
(Fig. 1d). Furthermore, the TEM image (Fig. S3a†) and element
mappings (Fig. S3b–h†) of the CsPbBr3@TiO-CN composite
exhibited a uniform dispersion of cesium, lead and bromine,
which indicates that the CsPbBr3 nanocrystals were homoge-
neously loaded on the TiO-CN nanosheets.
It is widely recognized that the connection pattern between
the components in a composite has an important effect on the
photogenerated carrier transfer properties of the composite.
Therefore, the interaction behavior of the CsPbBr3 nanocrystals
and the TiO-CN nanosheets was rst investigated with the aid of
Fourier transform infrared (FTIR) spectrum measurements. In
contrast to pristine TiO-CN with a strong characteristic
absorption band at ꢀ1241 cmꢁ1 (Fig. S4†)54 corresponding to
the typical stretching of C–N and C]N groups in TiO-CN, the
characteristic absorption band in CsPbBr3@TiO-CN displayed
an obviously reduced intensity, as presented in Fig. S4.† This
phenomenon indicated the existence of a strong bonding
interaction between NHx and Brꢁ correspondingly in TiO-CN
and CsPbBr3, originating from the easily formed ionic bonding.
The detailed chemical bonding behavior between CsPbBr3
and TiO-CN was further analyzed by performing high-resolution
X-ray photoelectron spectroscopy (XPS) measurements. The N
1s spectrum of TiO-CN could be resolved into four peaks, as
presented in Fig. 2a. Apart from the three typical peaks at 398.6,
399.5 and 401.2 eV for nitrogen in different chemical environ-
ments (C–N]C, N–(C)3, and NHx), there was a characteristic
peak at 404.5 eV in TiO-CN, which was attributed to the exis-
tence of C–N–H in the heterocycles, possessing positive charge
localization.55,56 It is worthwhile to note that this characteristic
peak at around 404.5 eV disappeared aer loading CsPbBr3 on
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Fig.
2 High-resolution XPS spectra of CsPbBr3, TiO-CN and
CsPbBr3@TiO-CN: (a) N 1s, (b) O 1s, (c) Br 3d and (d) Pb 4f.
TiO-CN, indicating that the localization of the positive charge
can be neutralized by the lone pair of electrons from Br on the
surface of CsPbBr3 by forming the chemical bond of C–N–Br. As
a result, the N 1s peaks in CsPbB3@TiO-CN showed a percep-
tible shi to the low-energy region with respect to that of pris-
tine TiO-CN, as observed in Fig. 2a. In addition, the XPS signal
for oxygen (Fig. 2b) in the TiO-CN component showed that the
binding energy of O 1s in CsPbB3@TiO-CN had clearly negative-
shied in comparison, suggesting the occurrence of a bonding
interaction between Br on the CsPbBr3 surface and OH in TiO-
CN. Therefore, loading CsPbBr3 on TiO-CN would result in
electron decient Br on the CsPbBr3 surface, which was further
demonstrated by the XPS signal of Br 3d. As shown in Fig. 2c,
the Br 3d5/2 and Br 3d3/2 peaks appeared at 68.2 and 69.2 eV in
pristine CsPbBr3 nanocrystals,57 which positively shied to 68.4
and 69.4 eV in CsPbBr3@TiO-CN, respectively. Subsequently,
the binding energies of Pb 4f7/2 and Pb 4f5/2 in CsPbB3@TiO-CN
also correspondingly shied to high energies from 138.4 and
143.2 eV to 138.6 and 143.5 eV, as illustrated in Fig. 2d.
For a typical photocatalyst, a good visible light response is
the most basic premise to achieve a visible-light-driven catalytic
reaction. Thereby, we rst evaluated the light-harvesting
capacity of the CsPbBr3@TiO-CN composite by recording the
electronic absorption spectra of CsPbBr3@TiO-CN to prelimi-
narily assess its application potential as a photocatalyst for CO2
reduction under the irradiation of visible light. As depicted in
Fig. 3a, loading the CsPbBr3 nanocrystals on the TiO-CN
nanosheets caused an augmented light response at a desir-
able longer wavelength compared to pristine TiO-CN owing to
the good light-harvesting capacity of CsPbBr3 in the visible
region (Fig. 3a). The photoresponse onset wavelength of
CsPbBr3@TiO-CN was red-shied from ꢀ460 nm to ꢀ550 nm.
Further, the Tauc plots of CsPbBr3 and TiO-CN are given in
Fig. 3b and c. The band gaps of CsPbBr3 and TiO-CN were ob-
tained from the intercepts of the extrapolation lines and energy
axes as 2.30 and 2.75 eV, respectively.
Fig. 3 (a) UV/Vis diffuse reflectance spectra of CsPbBr3, TiO-CN and
CsPbBr3@TiO-CN. Tauc plots of (b) CsPbBr3 and (c) TiO-CN. Mott–
Schottky plots of (d) CsPbBr3 and (e) TiO-CN. (f) Schematic illustration
of the band structures of CsPbBr3 and TiO-CN derived from the results
of flat-band potential and UV/Vis diffuse reflectance spectroscopy
measurements.
The energy-offset between the conduction band edges of
CsPbBr3 and TiO-CN plays a pivotal role in determining the
dynamic process of photogenerated electron transfer. Since the
conduction band edge potential is practically associated with
the at band potential in n-type semiconductors,58 herein, we
employed electrochemical measurements to evaluate the
conduction band edge of CsPbBr3 and TiO-CN by constructing
the Mott–Schottky plots, as depicted in Fig. 3d and e. The Mott–
Schottky plots of both CsPbBr3 and TiO-CN clearly exhibited
positive slopes, indicating that CsPbBr3 and TiO-CN were n-type
semiconductors. The at band potentials of CsPbBr3 and TiO-
CN were determined from the corresponding intercepts of the
linear plot region with the potential axis to be ꢁ1.00 and
ꢁ0.65 V vs. the normal hydrogen electrode (NHE), respectively,
which indicate that the photogenerated electrons in the
CsPbBr3 nanocrystals were transferred to the TiO-CN nano-
sheets, and the reduction reaction of CO2 to CO (ꢁ0.52 V vs.
NHE) by the photogenerated electrons in TiO-CN is thermody-
namically permitted. In addition, the corresponding valence
band edge potentials of CsPbBr3 and TiO-CN could be derived
from their band gaps and conduction-band edge potentials, as
1.30 and 2.10 V vs. NHE, as illustrated in Fig. 3f, indicating that
the photogenerated holes in the TiO-CN nanosheets could be
transferred to the CsPbBr3 nanocrystals, and the photo-
generated holes in the CsPbBr3 nanocrystals had enough
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driving force to trigger the water oxidation reaction to generate pristine CsPbBr3 nanocrystals was ꢀ14.8 ns, which is obviously
O2 (0.82 V vs. NHE).
larger than ꢀ8.4 ns for CsPbBr3@TiO-CN composites.
We speculated that the formation of chemical bonds and
The efficient charge separation between CsPbBr3 and TiO-CN
favorable energy-offsets between CsPbBr3 and TiO-CN would was further elucidated by electrochemical impedance spec-
facilitate the photogenerated electron transfer from CsPbBr3 to troscopy (EIS) and photocurrent response measurements. As
TiO-CN in the CsPbBr3@TiO-CN composite. To check out this, depicted in Fig. S5a,† the semicircular arc of the CsPbBr3@TiO-
steady state photoluminescence (PL) measurements were rstly CN composite exhibited an obviously smaller diameter in the
recorded to investigate the photoexcited electron transfer Nyquist plot compared to those of pristine CsPbBr3 and TiO-CN,
processes in the CsPbBr3@TiO-CN composite. Herein, pristine indicating the improvement in the separation efficiency of
CsPbBr3 was selected as the reference. As depicted in Fig. 4a, the photogenerated carriers in CsPbBr3@TiO-CN. In addition,
pristine CsPbBr3 nanocrystals exhibited a strong PL peak at a remarkably increased photocurrent density could also be
519 nm, and loading CsPbBr3 on the TiO-CN surface signi- detected, as presented in Fig. S5b,† which was over 2 and 3
cantly reduced the PL intensity, indicating the occurrence of times higher than those of the pristine CsPbBr3 and TiO-CN
a swi photogenerated electron transfer from CsPbBr3 to TiO- counterparts, respectively, conrming that combining
CN. Furthermore, we recorded the time-resolved photo- CsPbBr3 and TiO-CN substantially improved the photo-
luminescence (TRPL) traces of CsPbBr3 and CsPbBr3@TiO-CN generated carrier separation efficiency. These phenomena are
samples to scrutinize the photogenerated electron transfer in line with the results of the abovementioned steady state and
dynamics using the time-correlated single photon counting transient PL measurements.
technique (TCSPC), as shown in Fig. 4b. An excitation wave-
Efficient charge transfer and separation between CsPbBr3
length of 450 nm was picked to selectively excite CsPbBr3. The and TiO-CN in the CsPbBr3@TiO-CN composite improved the
dynamic PL trace of pristine CsPbBr3 (red symbols) in Fig. 4b photocatalytic performance, which was demonstrated by the
can be ascribed to the deactivation of the optically generated following photocatalytic measurements. The photocatalytic CO2
excitons in CsPbBr3 through radiative and nonradiative reduction reactions were carried out in CO2-saturated ethyl
processes. There was an obviously accelerated PL decay (blue acetate/water solution without additional sacricial reductants
symbols) aer loading CsPbBr3 on the surface of TiO-CN, under Xe-lamp irradiation with a 400 nm lter at the light
indicating the opening of a rapid electron transfer channel at intensity of 100 mW cmꢁ2. Herein, the reaction systems con-
the interface between CsPbBr3 and TiO-CN due to their tained a very small amount of water since the metal-halide
favourable energy-offset. These traces could be tted to a multi- perovskite is unstable when exposed to a large amount of
exponential function, and the tting parameters are listed in water.31 For all the evaluated pristine and composite photo-
Table S1.† The value of the amplitude-averaged lifetime of the catalyst samples, results from the chromatographic analysis
showed that the main product from CO2 reduction was CO
accompanied by a very small amount of CH4, and no other
reduction products such as H2 were detected. The product yield
of CO was plotted as a function of the photocatalysts, as pre-
sented in Fig. 5a. With pristine CsPbBr3 as the photocatalyst,
the yield of CO was only 38 mmol gꢁ1 aer 10 h of irradiation,
which is similar to the poor photocatalytic activity commonly
observed in the recent reports on pristine CsPbBr3-based pho-
tocatalysts.20,22,24,27,29,31 On the other hand, pristine TiO-CN also
showed very inferior photocatalytic activity with a low CO yield
of 19 mmol gꢁ1 from CO2 reduction under the same irradiation
time, as presented in Fig. 5a, which may be ascribed to weak
light absorption in the visible region and inferior charge
separation.
It should be noted that combining CsPbBr3 with TiO-CN
indeed boosts the photocatalytic activity in CO2 reduction to
CO owing to improved charge separation and an increased
number of catalytic sites. As shown in Fig. 5a, the CsPbBr3@-
TiO-CN composite exhibited a signicantly improved yield of
129 mmol gꢁ1 for CO formation aer 10 h of irradiation, which is
over 3 and 6 times higher than those of pristine CsPbBr3 and
TiO-CN, respectively. We also found that the CsPbBr3 content
on the surface TiO-CN plays a pivotal role in the photocatalytic
performance of CsPbBr3@TiO-CN composite, exhibiting
a volcano-type trend, as depicted in Fig. S6.† A lower loading
Fig. 4 (a) Photoluminescence spectra of CsPbBr3 and CsPbBr3@TiO-
CN. (b) Time-resolved photoluminescence decays of CsPbBr3 and
amount of CsPbBr3 on TiO-CN led to weak light absorption,
resulting in a lower yield of CO product for CsPbBr3@TiO-CN.
CsPbBr3@TiO-CN. The gray curves are the fitting lines based on
a multi-exponential function.
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The origin of the reduction product CO was further
conrmed by a control experiment. In an isotope labelling
experiment with 13CO2 replacing 12CO2 as the feedstock, gas
chromatography/mass spectrometry analysis could clearly
identify the major reaction product 13CO (m/z ¼ 29), as shown in
Fig. 5b, conrming that the CO was mainly generated from
visible-light-driven CO2 reduction and not the photo-oxidation
of ethyl acetate. On the other hand, the oxidation product O2
could also be detected along with CO in the chromatographic
analysis results, which is consistent with the common obser-
vation in CsPbBr3-based photocatalyst systems.20,27,31 To further
verify the origin of the oxidation product O2, an isotope trace
experiment with H218O was performed in a CO2-saturated ethyl
acetate/H218O solution with CsPbBr3@TiO-CN as the photo-
catalyst. A major mass signal of 18O2 with an m/z value of 36
could be clearly detected, as presented in Fig. 5c, indicating that
O2 originates from the water oxidation reaction by consuming
the photogenerated holes in the CsPbBr3@TiO-CN composite,
which demonstrates that water is the main electron source for
the photocatalytic reduction of CO2 to CO.
Conclusions
In summary, we successfully fabricated a CsPbBr3@TiO-CN
composite based on a facile process, which can be employed
as an efficient photocatalyst for visible-light-driven CO2 reduc-
tion using water as the electron source. This composite photo-
catalyst could achieve a signicant improvement in CO
conversion yield from CO2, which is over 3 and 6 times higher
than those of pristine CsPbBr3 and TiO-CN, respectively.
Microstructure characterization revealed that the CsPbBr3
nanocrystals were closely anchored on 2D TiO-CN via N–Br and
O–Br bonding. Combining CsPbBr3 with TiO-CN led to an
obviously enhanced of photogenerated carrier separation effi-
ciency, as disclosed by the steady-state and transient photo-
luminescence data, as well as electrochemical measurements.
We also observed the pivotal role of the metal anion in
enhancing the photocatalytic activity of the catalyst in CO2
reduction, providing a clear clue for further design of metal-
halide perovskite-based photocatalysts through material
engineering.
Fig. 5 (a) The yields of CO generated from the photocatalytic CO2
reduction reactions with TiO-CN, CsPbBr3, CsPbBr3@g-C3N4 and
CsPbBr3@TiO-CN photocatalysts after 10 h of irradiation under
a 300 W Xe-lamp with the light intensity of 100 mW cmꢁ2. Gas
chromatograms and mass spectra (GC-MS) of the solar-driven (b)
reduction of 13CO2 to 13CO (m/z ¼ 29) and (c) oxidation of H218O to
18O2 (m/z ¼ 36) using CsPbBr3@TiO-CN as the photocatalyst.
The lower yield of CO product for CsPbBr3@TiO-CN with
a higher loading amount of CsPbBr3 may be ascribed to the
increased amount of CsPbBr3 without chemical bonding with
TiO-CN, resulting in accelerated charge recombination through
the surface defect states in CsPbBr3. Moreover, to assess the
superiority of titanium implantation in g-C3N4, we prepared
a control sample with CsPbB3 nanocrystals anchored on 2D g-
C3N4 (coded as CsPbBr3@g-C3N4) without titanium implanta-
tion. Fig. 5a shows that the yield of CO from CO2 reduction in
the case of CsPbBr3@g-C3N4 was only little higher compared to
that of pristine CsPbBr3 under the same light irradiation
condition, which is about 3 times lower than that of the
CsPbBr3@TiO-CN composite owing to the lack of effective
catalytic sites on g-C3N4, unlike TiO-CN.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
This work was nancially supported by Natural Science Foun-
dation of Tianjin City (17JCJQJC43800), National Key R&D
Program of China (2017YFA0700104), NSFC (21790052) and the
111 Project (D17003).
Notes and references
1 X. Li, J. Yu, M. Jaroniec and X. Chen, Chem. Rev., 2019, 119,
3962–4179.
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This journal is © The Royal Society of Chemistry 2019

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´
´
2 J. H. Montoya, L. C. Seitz, P. Chakthranont, A. Vojvodic, 26 H. Huang, H. Yuan, K. P. F. Janssen, G. Solıs-Fernandez,
T. F. Jaramillo and J. K. Nørskov, Nat. Mater., 2017, 16, 70–81.
3 K. K. Sakimoto, A. B. Wong and P. Yang, Science, 2016, 351,
74–77.
Y. Wang, C. Y. X. Tan, D. Jonckheere, E. Debroye, J. Long,
J. Hendrix, J. Hoens, J. A. Steele and M. B. J. Roeffaers,
ACS Energy Lett., 2018, 3, 755–759.
4 J. L. White, M. F. Baruch, J. E. Pander III, Y. Hu, 27 Z.-C. Kong, J.-F. Liao, Y.-J. Dong, Y.-F. Xu, H.-Y. Chen,
I. C. Fortmeyer, J. E. Park, T. Zhang, K. Liao, J. Gu, Y. Yan,
T. W. Shaw, E. Abelev and A. B. Bocarsly, Chem. Rev., 2015,
115, 12888–12935.
D.-B. Kuang and C.-Y. Su, ACS Energy Lett., 2018, 3, 2656–
2662.
28 S. Park, W. J. Chang, C. W. Lee, S. Park, H.-Y. Ahn and
K. T. Nam, Nat. Energy, 2016, 2, 16185.
`
˜
5 S. Berardi, S. Drouet, L. Francas, C. Gimbert-Surinach,
M. Guttentag, C. Richmond, T. Stoll and A. Llobet, Chem. 29 Y.-F. Xu, M.-Z. Yang, B.-X. Chen, X.-D. Wang, H.-Y. Chen,
Soc. Rev., 2014, 43, 7501–7519.
6 K. C. Christoforidis and P. Fornasiero, ChemCatChem, 2019,
11, 368–382.
D.-B. Kuang and C.-Y. Su, J. Am. Chem. Soc., 2017, 139,
5660–5663.
¨
¨
30 K. Chen, X. Deng, G. Dodekatos and H. Tuysuz, J. Am. Chem.
7 X. Chen and F. Jin, Front. Energy, 2019, 13, 207–220.
Soc., 2017, 139, 12267–12273.
8 D. C. Grills, M. Z. Ertem, M. McKinnon, K. T. Ngo and 31 J. Hou, S. Cao, Y. Wu, Z. Gao, F. Liang, Y. Sun, Z. Lin and
J. Rochford, Coord. Chem. Rev., 2018, 374, 173–217. L. Sun, Chem.–Eur. J., 2017, 23, 9481–9485.
9 H. Takeda, C. Cometto, O. Ishitani and M. Robert, ACS 32 Q. A. Akkerman, G. Raino, M. V. Kovalenko and L. Manna,
Catal., 2017, 7, 70–88. Nat. Mater., 2018, 17, 394–405.
10 C. Li, Y. Xu, W. Tu, G. Chen and R. Xu, Green Chem., 2017, 19, 33 M. V. Kovalenko, L. Protesescu and M. I. Bodnarchuk,
882–899. Science, 2017, 358, 745–750.
11 H. Abdullah, M. M. R. Khan, H. R. Ong and Z. Yaakob, J. CO2 34 L. Polavarapu, B. Nickel, J. Feldmann and A. S. Urban, Adv.
Util., 2017, 22, 15–32. Energy Mater., 2017, 7, 1700267.
12 Z.-F. Huang, J. Song, L. Pan, X. Zhang, L. Wang and J.-J. Zou, 35 X. Li, F. Cao, D. Yu, J. Chen, Z. Sun, Y. Shen, Y. Zhu, L. Wang,
Adv. Mater., 2015, 27, 5309–5327. Y. Wei, Y. Wu and H. Zeng, Small, 2017, 13, 1603996.
13 Y. Ma, X. Wang, Y. Jia, X. Chen, H. Han and C. Li, Chem. Rev., 36 Q. Zhang and Y. Yin, ACS Cent. Sci., 2018, 4, 668–679.
`
2014, 114, 9987–10043.
14 S. N. Habisreutinger, L. Schmidt-Mende and J. K. Stolarczyk,
Angew. Chem., Int. Ed., 2013, 52, 7372–7408.
37 L. N. Quan, F. P. G. de Arquer, R. P. Sabatini and
E. H. Sargent, Adv. Mater., 2018, 30, 1801996.
38 M. Ahmadi, T. Wu and B. Hu, Adv. Mater., 2017, 29, 1605242.
15 J. Wang, T. Xia, L. Wang, X. Zheng, Z. Qi, C. Gao, J. Zhu, Z. Li, 39 S. A. Veldhuis, P. P. Boix, N. Yantara, M. Li, T. C. Sum,
H. Xu and Y. Xiong, Angew. Chem., Int. Ed., 2018, 57, 16447–
16451.
N. Mathews and S. G. Mhaisalkar, Adv. Mater., 2016, 28,
6804–6834.
16 M. F. Kuehnel, C. D. Sahm, G. Neri, J. R. Lee, K. L. Orchard, 40 S. Tian, Z. Wang, W. Gong, W. Chen, Q. Feng, Q. Xu, C. Chen,
A. J. Cowan and E. Reisner, Chem. Sci., 2018, 9, 2501–2509.
17 M. F. Kuehnel, K. L. Orchard, K. E. Dalle and E. Reisner, J.
Am. Chem. Soc., 2017, 139, 7217–7223.
18 R. D. Harris, S. B. Homan, M. Kodaimati, C. He,
A. B. Nepomnyashchii, N. K. Swenson, S. C. Lian,
C. Chen, Q. Peng, L. Gu, H. Zhao, P. Hu, D. Wang and Y. Li, J.
Am. Chem. Soc., 2018, 140, 11161–11164.
41 P. Huang, J. Huang, S. A. Pantovich, A. D. Carl, T. G. Fenton,
C. A. Caputo, R. L. Grimm, A. I. Frenkel and G. Li, J. Am.
Chem. Soc., 2018, 140, 16042–16047.
R. Calzada and E. A. Weiss, Chem. Rev., 2016, 116, 12865– 42 X. Wang, W. Wang, M. Qiao, G. Wu, W. Chen, T. Yuan, Q. Xu,
12919.
M. Chen, Y. Zhang, X. Wang, J. Wang, J. Ge, X. Hong, Y. Li,
Y. Wu and Y. Li, Sci. Bull., 2018, 63, 1246–1253.
43 M. Ou, S. Wan, Q. Zhong, S. Zhang and Y. Wang, Int. J.
Hydrocarbon Eng., 2017, 42, 27043–27054.
19 X. Zhu, Y. Lin, J. S. Martin, Y. Sun, D. Zhu and Y. Yan, Nat.
Commun., 2019, 10, 2843.
20 L.-Y. Wu, Y.-F. Mu, X.-X. Guo, W. Zhang, Z.-M. Zhang,
M. Zhang and T.-B. Lu, Angew. Chem., Int. Ed., 2019, 58, 44 W. Liu, L. Cao, W. Cheng, Y. Cao, X. Liu, W. Zhang, X. Mou,
9491–9495.
L. Jin, X. Zheng, W. Che, Q. Liu, T. Yao and S. Wei, Angew.
Chem., Int. Ed., 2017, 56, 9312–9317.
45 G. Gao, Y. Jiao, E. R. Waclawik and A. Du, J. Am. Chem. Soc.,
2016, 138, 6292–6297.
21 X. Zhu, Y. Lin, Y. Sun, M. C. Beard and Y. Yan, J. Am. Chem.
Soc., 2019, 141, 733–738.
22 M. Ou, W. Tu, S. Yin, W. Xing, S. Wu, H. Wang, S. Wan,
Q. Zhong and R. Xu, Angew. Chem., Int. Ed., 2018, 57, 46 X. Li, W. Bi, L. Zhang, S. Tao, W. Chu, Q. Zhang, Y. Luo,
13570–13574. C. Wu and Y. Xie, Adv. Mater., 2016, 28, 2427–2431.
23 Y.-F. Xu, X.-D. Wang, J.-F. Liao, B.-X. Chen, H.-Y. Chen and 47 S. Tang, X. Yin, G. Wang, X. Lu and T. Lu, Nano Res., 2019, 12,
D.-B. Kuang, Adv. Mater. Interfaces, 2018, 5, 1801015. 457–462.
24 Y.-F. Xu, M.-Z. Yang, H.-Y. Chen, J.-F. Liao, X.-D. Wang and 48 Y. Zhu, T. Wang, T. Xu, Y. Li and C. Wang, Appl. Surf. Sci.,
D.-B. Kuang, ACS Appl. Energy Mater., 2018, 1, 5083–5089. 2019, 464, 36–42.
25 Y. Wu, P. Wang, X. Zhu, Q. Zhang, Z. Wang, Y. Liu, G. Zou, 49 G. Shi, L. Yang, Z. Liu, X. Chen, J. Zhou and Y. Yu, Appl. Surf.
Y. Dai, M.-H. Whangbo and B. Huang, Adv. Mater., 2018,
30, 1704342.
Sci., 2018, 427, 1165–1173.
50 H. Li, Y. Gao, Z. Xiong, C. Liao and K. Shih, Appl. Surf. Sci.,
2018, 439, 552–559.
This journal is © The Royal Society of Chemistry 2019
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View Article Online
RSC Advances
Paper
51 X. Lu, K. Xu, S. Tao, Z. Shao, X. Peng, W. Bi, P. Chen, H. Ding, 55 J. Fu, B. Zhu, C. Jiang, B. Cheng, W. You and J. Yu, Small,
W. Chu, C. Wu and Y. Xie, Chem. Sci., 2016, 7, 1462–1467. 2017, 13, 1603938.
52 J. Li, L. Xu, T. Wang, J. Song, J. Chen, J. Xue, Y. Dong, B. Cai, 56 P. Yang, H. Ou, Y. Fang and X. Wang, Angew. Chem., Int. Ed.,
Q. Shan, B. Han and H. Zeng, Adv. Mater., 2017, 29, 1603885. 2017, 56, 3992–3996.
53 J. Song, J. Li, L. Xu, J. Li, F. Zhang, B. Han, Q. Shan and 57 J. Liang, C. Wang, Y. Wang, Z. Xu, Z. Lu, Y. Ma, H. Zhu,
H. Zeng, Adv. Mater., 2018, 30, 1800764.
54 M. Ou, S. Wan, Q. Zhong, S. Zhang, Y. Song, L. Guo, W. Cai
and Y. Xu, Appl. Catal., B, 2018, 221, 97–107.
Y. Hu, C. Xiao, X. Yi, G. Zhu, H. Lv, L. Ma, T. Chen, Z. Tie,
Z. Jin and J. Liu, J. Am. Chem. Soc., 2016, 138, 15829–15832.
58 C. Baumanis and D. W. Bahnemann, J. Phys. Chem. C, 2008,
112, 19097–19101.
34348 | RSC Adv., 2019, 9, 34342–34348
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